1. Field of the Invention
The present invention relates to a magnetic tape recorder for recoding video signals, and audio signals if any, on a magnetic tape and, more particularly, to a video tape recorder having an end-to-end joint-recording capability and a video camera in which such a video tape recorder is built in. The word "joint-recording" used herein refers to recording on a magnetic tape a sequence of video signals which are representative of a certain scene immediately after a preceding sequence of video signals representative of a different scene without disturbing synchronization.
2. Description of the Related Art
Many of the modern video tape recorders, such as recorders for family use adopt a helical scanning system. A helical can type video tape recorder which has an end-to-end joint-recording capability as defined above has customarily been constructed to transport a magnetic tape, or a video tape, backward by a small amount at the end of a recording so as to prepare for the next recording. This conventional approach has been successful in promoting sure tracking of magnetic heads of the recorder to a particular track of a magnetic tape in which an immediately preceding recording is stored in the form of video signals, as soon as the recorder begins to operate for another recording.
However, such conventional video tape recorders as described above suffer from a drawback that unexpected video signals are written in an end portion of a preceding recording under disturbed synchronization. Specifically, assume that when a sequence of video signals representative of a certain scene are being recorded on a magnetic tape, a trigger switch for joint-recording such as a record/playback button is operated at a certain position on the tape. Then, the recording operation is immediately stopped, but the tape is caused to run by an extra length due to inertia until a tape transport mechanism of the recorder fully stops its motion, which brings about the problem stated above.
Another problem with such conventional video tape recorders is the time lag which exists between the entry of a joint-record command and the establishment of servo-lock. After the tape transport mechanism has been brought into a stop as mentioned above, the video tape is fed backward by a predetermined length and then fed forward to stop at a predetermined position. At this position, the recorder assumes a record pause status, for example, and awaits the next operation of the trigger switch. Upon the next operation of the trigger switch, the tape begins to run. Specifically, a capstan of the tape transport mechanism is rotated while, at the same time, a head cylinder carrying magnetic heads therewith is rotated. After servo-lock has been established at a certain position on the tape, another sequence of video signals are recorded on the tape in adequate synchronism. However, a certain period of time is necessary for the servo-lock to be actually established after the entry of the joint-record command. Consequently, a substantial period of time such as 1 second inclusive of the above period of time expires after the entry of the joint-record command. The waste of 1 second or so after the entry of a joint-record command is critical in shooting a desired scene by a camera.